Control system for aligning or turning longwall faces in mine workings lined with walking casing frames



Dec. 9, 1969 o. JACOBI 3, 8 ,87

CONTROL SYSTEM FOR ALIGNING OR TURNING LONGWALL FACES IN MINE WORKINGS LINED WITH WALKING CASING FRAMES Filed May 29, 1968 2 Sheets-Sheet 1 Dec. 9., 1969 o. JACOBI 3, 8 ,877

CONTROL SYSTEM FOR ALIGNING OR TURNING LONGWAL-L FACES IN MINE WORKINGS LINED WITH WALKING CASING FRAMES Filed May 29, 1968 2 Sheets-Sheet 2 United States Patent O 3,482,877 CONTROL SYSTEM FOR ALIGNING OR TURNING LONGWALL FACES IN MINE WORKINGS LINED WITH WALKING CASING FRAMES Oskar Jacobi, Blankenstein, Germany, assignor to Bergwerksverband GmbI-I, Essen, Germany, a corporation of Germany Filed May 29, 1968, Ser. No. 732,976 Claims priority, application Germany, May 31, 1967, B 92,791 Int. Cl. E21c 1/00 US. Cl. 299-1 6 Claims ABSTRACT OF THE DISCLOSURE The invention relates to a control system for aligning or turning longwall faces in mine workings lined with walking casing structures and equipped With extraction machinery, in particular a coal-cutting machine, which control system, by control of the point of pivoting of the coal-cutting machine in the Working and/ or of the pressure it exerts through certain feed mechanisms, determines the advance of a local Zone of the face and therefore the alignment or turning of the face as a whole, the control arrangements which govern the turning movement or govern the feed mechanisms being supplied with input quantities or signals which reproduce the deviation of the line of the face from a theoretical position, thereby to straighten the working generally whilst allowing for local deviations up to a predetermined maximum.

BACKGROUND OF THE INVENTION It is Well known to use local inspection of the line of the working face or of the conveyor as a basis on which manually to operate or cut out the feed mechanisms or to locally reverse the extraction machinery at the end of zones of the face which have been left unworked or which are intended to be covered when a turning operation is carried out. This kind of approach cannot be used where unmanned, i.e. automatic, working of the face is being planned or being carried out; furthermore, it has the drawback that it prevents optimum advances into the face from being achieved.

OBJECT OF THE INVENTION It is the purpose of the invention to provide a control system which will align or turn the face substantially automatically and therefore improve the reliability of operation of the mine working and also the safety thereof, even in the case of large advances into the face.

It is a more specific object of the present invention to create a device which more or less continually detects the line of the face and aligns or turns it to coincide with a predetermined line.

BRIEF SUMMARY OF THE INVENTION This object is realised, in accordance with the basic principle of the invention, by virtue of the fact that the input quantities or signals determine limiting values any exceeding of which is in effect continuously detected, the limiting values for the alignment of the face being assumed to be constant (or differing to predetermined extents in the case where the face is being turned), and by virtue of the fact that the input quantities or signals simulate the differences between the distances travelled by the casing structures in the local zones of the face, the relevant input quantities being applied to the stepping mechanism or the turning control mechanism, as the case may be.

Unlike the known process, control is no longer effected upon the basis of the curvature of the face of the working or of the conveyor, but upon the basis of the deviation of the casing structures from a predetermined alignment. The introduction of predetermined limiting values for the input quantities provides the control system with a threshold of perception, as will be explained hereinafter. This permits safe deviations of the casing structures from their predetermined line, without giving rise to actuation of the control system. Local deviations in the position of the conveyor or in the line of the Working face are allowed to develop unless they cause the said threshold to be exceeded.

Equally, the casing structures themselves can be controlled by the face of the working. In this way, the dam aging influence which can be exerted on the line of the Working by local curvature in the face can be corrected in good time.

In no circumstances can the working become misaligned beyond a certain permissible extent, because the face is straightened up by the control system before any dangerous situation can develop, or the face is turned.

In other words, if a part of a face is leading the rest, using the control system in accordance with the invention the feed mechanisms (for example in the form of feed cylinders) can be rendered inoperative until the neighbouring, lagging sections of the face, in which the feed mechanisms are still operative, have caught up. In this context, the hitherto manually operated valves of the feed cylinders can be replaced by pneumatic servo controls without any difliculty, the input quantities or signals being fed to these controls.

FURTHER FEATURES OF THE INVENTION The invention can be simplified if, in accordance with a further feature, the controls of several neighbouring feed mechanisms appertaining to casing structures covering a largish section of the face are associated and supplied with the same input quantities, since then larger spans of the face can be aligned in accordance with the same control criteria, the control quantity or signal only having to be determined once for each face section.

The system in accordance with the invention measures the extent to which the face is off line (signalled by the input quantities exceeding the limiting value) by virtue of the fact that the distances advanced by the casing structures are determined. The fundamental principle is that an imaginary zero line is laid along the face and measurements made from each casing structure (or groups of associated structures) to this line. This overcomes the problematical operation of measuring curvature in the face.

This determination of the input quantities is most simply effected if the casing structures always feed forward by the same incremental distance. Then, all that is necessary is to allocate stepping counters to the structures for measuring the advance, and, in relation to a guide casing structure in a group of associated structures, to determine a difference value for a group of neighbouring casing structures. This value is then either fed into the control of the feed mechanisms locally allocated to the group, or supplied to a turning control mechanism, which latter must then of course be provided with information regarding the limits of movement of the individual structures of the. group.

If, however, the incremental movements of the casing structures are not constant, then in addition to the counter a device must be provided for measuring the feed dis tance. The calculation of the difference value, and therefore of the appropriate input quantity or signal, is carried out by a digital or analogue computer.

In this context, analogue computers may take the form of simple mechanical equipment or logic components of electrical, pneumatic or hydraulic design, connected in the control line of the casing system. Computer devices of this kind are generally substantially simpler than digital computers and can be accommodated directly in the casings.

The fundamental principle of difference-formation, upon which the invention is based, also applied when the face is being turned. In this case, the procedure can be that the guide casing structure executes one step, whilst one or more of the neighbouring structures in the group executes 11 steps. The difference between the steps executed by this or these other casing structure or structures, and the single step executed by the guide casing structure, must be zero. If the difference is less than zero, then the feed cylinder associated with the guide casing structure must be rendered inoperative, whilst if it is greater than zero then the feed cylinder of the corresponding casing structure. must be rendered inoperative.

Self-evidently, in all cases precautions must be taken to ensure that errors due to manufacturing tolerances and tolerances of measurement, which may occur in the measured values, are not additive, i.e. the stepping counters and the devices for measuring the distances of the feeds must be capable of being corrected from time to time.

The device may be improved by the provision of instruments for indicating local auxiliary quantities or indicating which of the feed cylinders are operative, in order to reverse the extraction machinery at the limits of the zones of the. face which are exhibiting excessive deviation. The operator controlling the extraction machinery can then arrange for it to cut the un-worked zones of the face several times, these being the zones at which the feed cylinders have been correspondingly operated. This also means that it is possible, by the automatic introduction, of the values indicating the excess over the limiting values, into the reversing control of the extraction machinery, to control the aforedescribed cuttingoperation completely automatically.

The advantage of the control system in accordance with the invention accordingly resides in the fact that the worked face is held in a predetermined line or turned on to such line, although local (safe) deviations of the face of the working from this line are permissible. 'Ihe equipment and devices needed to create the control system in accordance with the invention are extremely simple and can readily be incorporated into the existing control mechanisms appertaining to the casing structures or groups thereof which form the casing system of the working.

DESCRIPTION OF DRAWINGS The invention may be carried into practice in various ways but a practical example thereof will now be described with reference to the accompanying drawing, in which:

FIGURE 1 schematically illustrates, in plan view, a mine working employing extraction machinery including a conveyor and a casing system which is cut-away to show a control system in accordance with the invention; and

FIGURE 2 shows a preferred embodiment of a comparator device for use in the control system according to the invention.

In FIGURE 1, the reference 1 designates a coal-face. at which extraction machinery, in the form of a coal-cutter 3, is moved backwards and forwards in front of the coalface 1 by a chain 2. The coal cut out by the cutter 3 falls automatically onto a double-chain conveyor 4 of known kind which is for simplicity shown as a chain carrying slats 5. The drive arrangements for the cutter 3 and the conveyor 4 have not been illustrated.

The mine working is lined with a walking casing frame system. The walking casing frame system consists, in this particular example, of easing frames or trusses 8, each in corporating four pit props 9. Each casing frame 8 is provided with a double-acting feed cylinder 11, attached at the point 10, the piston rod 12 of which is in each case attached to the conveyor 4,

If the feed cylinders are operated to retract the piston rod, the pit props 9 of the appropriate casing frame. 8 having been unloaded, then the frame 8 moves up towards the conveyor. If the feed cylinder 11 is operated in the reverse direction, i.e. the piston rod 12 is extended, then the conveyor 4 is moved up towards the face 1 of the mine working so that the cutter 3 is set to a selected depth of cut 14.

If, on the other hand, the cylinders 11 are rendered inoperative, then the cutter 3 is not set to any depth of cut at all and therefore cuts no coal from the face 1.

Accordingly, it will be understood that, in accordance with how the feed cylinders 11 are controlled at local zones of the face, e.g. at the zone illustrated, which has five casing frames, the face. 1 of the working can be advancd beyond or held back in relation to the faces in neighbouring zones of the working. For automatic control for this purpose, the feed cylinders 11 require to be fed with appropriate input control quantities or signals determining how the feed cylinders 11 are operated at the local zones of the face.

To this end, the five casing frames 8, 8a, 8b, 8c, 8d, include one guide casing frame 8b. It is assumed that the feed increments of the other frames 8, 8a, and 8d are to be the same.

The control system for the grouped casing frames 8 to 8d includes a group switching arrangement 20 which, in a predetermined sequence and via lines 21 to 24 respectively allotted to the casing frames 8 to 8d with the exception of the guide casing frame 8b, passes control pulses to comparator controls 25, 26, 27 and 28, one of which is allotted to each of the casing frames 8, 8a, 80 and 8d. The guide casing frame 81) is connected in parallel with the comparator controls 25 to 28, through lines 31, 32 and 33.

One of the comparator controls 25 to 28, all of which are identically arranged, is schematically illustrated in FIGURE 2.

A cam-shaft 40 is mounted in bearings 41 and 42 and is rotated in one sense by a piston rod 44 driven from a cylinder/piston device 43 and in the other sense by a piston rod 46 driven from a cylinder/piston device 45. The input to the comparator control is provided by a line 21 leading from the group switching arrangement 20. There is also an output line 21a in which appears an input control quantity in the form of a pulse for controlling the feed cylinder 11.

As soon as the group switching arrangement 20 selects the casing frame 8 for operation and therefore causes a control pulse to appear in the line 21, the cylinder/piston device 43 is appropriately pressurised and rotates the camshaft 40 through a certain angle, causing a cam 47 to operate and close a valve 48. However, the control pulse also passes through a further valve 49 into the line 21a and causes the casing frame 8 to advance one step. Simultaneously, through a branch line 21b the pulse is fed to an indicator 210 for showing that the control pulse has been issued.

A further control pulse from the group switching arrangement 21 leads to a second operation of the cylinder/ piston device 43 and thus to further rotation of the camshaft 40, so that a valve 49 is closed by a cam 50, the valve 48 being kept closed also. The signal will also appear in the line 21a so that the casing frame 8 will advance a further step.

Any further signal from the group switching arrangement fails to produce further rotation of the cam-shaft 40 since the piston rod 44 is now fully extended by the cylinder/piston device 43.

The two rotational movements in the one sense on the part of the cam-shaft 40 have left unchanged the position of valves 51 and 52 respectively associated with cams 53 and 54.

If pulses now appear in a line 33 leading from the guide casing frame 812, the first one causes the cam-shaft 40 to rotate in the opposite sense, closing the valve 51 and cans ing the guide casing frame 8b to execute one step. This is also indicated via a line 32a leading to an indicating instrument 32b.

When the valve 51 has been operated, the cam-shaft simultaneously returns the valve 49 to its initial position. When a second pulse originating from the guide casing frame 8b closes the valve 52 at the right-hand side of the comparator, the valve 48 at the left-hand side is closed. If a third pulse now appears in the line 33, the connection to the guide casing frame 8b is closed, and this casing frame 8b cannot execute another step.

It can be seen, therefore, that the casing frames 8, 8a and 8c, 8d can lead the guide casing frame 8b by a maximum of two steps. This facility for two steps defines the threshold of perception" of the control system, which then intervenes in the manner described and re-establishes alignment between all the casing frames. Accordingly, the coal-face is continually aligned between these limiting values.

I claim:

1. In a mine working having extraction machinery for working a longwall face and a self-advancing casing structure system, a control system for reorientating the longwall face comprising:

measuring means operative to determine the distances of individual casing structures, in different zones along the face, from a nominal line of working;

signal generating means operative to generate control signals in accordance with the differences in said measured distances;

means responsive to said control signals to determine when the said differences in measured distances respectively exceed at least one predetermined limiting value;

a switching arrangement for selectively distributing the said control signals to the individual casing structures to trigger the drive mechanisms thereof;

and means whereby the said drive mechanisms are triggered only when the said differences in measured distances exceed the limiting value.

2. A control system according to claim 1, for a mine working in which pluralities of individual casing structures are associated in groups, each group being common to a zone of the face, wherein the measuring means is operative to measure the distances of individual casing structures serving as guides, one in each group, from the nominal line of working.

3. A control system according to claim 2, including secondary measuring means operative to determine the distances between the guide casing structure in a group and the other casing structures in the group, secondary signal generating means operative to generate auxiliary signals in accordance with said further measured distances, and a secondary switching device for selectively distributing the auxiliary signals to the said other casing structures in the group to trigger the drive mechanisms thereof.

4. A control system according to claim 1, including devices for distance measurement cooperating with stepping counters to determine the distances moved by the casing structures, and a computer governing generation of the signals fed to the drive mechanisms of the casing structures.

5. A control system according to claim 1, including means for indicating that one of the said measured distance differences has exceeded a predetermined limiting value, and means for additionally feeding the control signal to the extraction machinery to control the operation thereof at the zone of the face whereat the exceeding of the limiting value has occurred.

6. A control system according to claim 5, wherein the said feeding means leads to the turning control mechanism of the extraction machinery.

References Cited UNITED STATES PATENTS 3,362,750 1/1968 Carnegie 2991 FOREIGN PATENTS 1,095,543 12/1967 Great Britain.

ERNEST R. PURSER, Primary Examiner US. Cl. X.R. 6l45.2 

